Phase control system



July 6, 1937. E. H. ARMSTRONG. 2,085,940

PHASE CONTROL SYSTEM Filed Sept. 14, 1955 I N VENTOR.

Edw/h H. Armsfronq.

ATTORNEYS.

Patented July 6, 1937 UNITED STATES PATENT OFFICE 2,085,940 PHASECONTROL SYSTEM Edwin H. Armstrong, New York, N. Y.

Application September 14, 1935, Serial No. 40,546

2 Claims.

may be readily obtained. The general arrangel figure of the accompanyingdrawing. figure, l represents the input current whose phase it isdesired to alter. 2, 3, 4, 5, and 6, i represent three branch circuitseach consisting of equal 20 high resistances, 2, 4, and 6. In serieswith resistance 2 is a capacity 3, in series with resistance e is aresistance 5, and in series with resistance 6 is an inductance I. Theimpedances of the capacity 3, resistance 5 and inductance l. are alladjusted to be equal in the frequency to be employed. Three vacuum tubes8, 9, and I have applied to their grids, respectively, the voltagesexisting across the capacity-3, the resistance and the inductance 1.Three equal 0 resistances H, l2, and I3 are inserted in the platecircuits'of these tubes. Connecting the points A with B and B with C areequal high resistances forming a potentiometer arrangement between thesethree plates. Connected be- 5 tween the midpoint of the resistanceconnecting points A and B and the junction point of the threeresistances ll, l2, and I3 is a high resistance l6. Similarly connectedto the midpoint of the resistance connecting points B and C is 40 a highresistance whose other terminal goes to the junction point of theresistances H, l2, and I3. The output circuit is taken between thejunction points of the resistances II, I2 and I3 and point P on thepotentiometer. The operation of 45 the system is as follows:

The voltages at the three points A, B, and C taken across theresistances ll, l2, and I3, respectively, are 90 apart from each other,C lead- 50 ing point B by 90 and A lagging behind point B by 90. Sincethe resistances are all equal and the impedances of 3, 5, and I areequal, the voltages at the points A, B, and C are equal to each other.The resistances l4, l6 and I5, I! are made 55 sufiiciently high withrespect to the resistances ment of the system is illustrated in thesingle In this H, l2 and l3 that their effect on the impedances in theplate circuit is negligible.

By proportioning resistance l6 with respect to the value of resistancel4 it is possible to bring point D midway in phase between points A andB, 5 that is, 45 from either of them and equal in amplitude to either ofthese voltages. Similarly, it is possible by adjustment of resistance I1with respect to resistance l5 to produce the same phase and amplituderelations at point'E. These five points on the potentiometer aretherefore definitely fixed 45 apart and all of equal amplitude. Aspotentiometer point P travels along the potentiometer it will passgradually through any degree of phase relationship which may be desired.The variation in amplitude at those points on the potentiometer whichare not definitely fixed will be very slight from the average value, butif it is desired more points on the potentiometer may have theiramplitudes definitely fixed and the degree of variation reduced therebybelow any desired limits. It will be observed that in eiiect thisarrangement corresponds to a tapered potentiometer, the variations inthe resistance of the potentiometer compensating for the changes inamplitude which would occur as the pointer is moved around thepotentiometer.

. While I have illustrated three voltages spaced 90 apart it will ofcourse be understood that other values of spacing may be used and thatwhere an adjustment of phase of less than 180 is required two voltagesmay be all that is required. Various other modifications andcombinations may be employed without departing from the spirit of theinvention. I

I claim:

1. A system for adjusting the phase of an alternating current withoutsimultaneously producing a change in its amplitude, comprising a seriesof vacuum tubes, means for dividing an 40 alternating current into aseries of currents successively difiering in phase by the same amount,means for each of said currents for equalizing the voltages derivedtherefrom and for selectively impressing them on the input of, a vacuumtube, a tapered potentiometer-and means for connecting the output sidesof said tubes to points on said potentiometer diiiering from each otherin phase by the same amount, the amount of impedance introduced into theoutput circuit of each tube by the potentiometer being substantiallyequal, said potentiometer having means for selectively deriving currenttherefrom.

2. Apparatus for adjusting the phase of an alternating current withoutsimultaneously profor combining the output voltages of the vacuum tubes;the amount of impedance introduced into the output circuit of each tubeby the potentlometer being substantially equal, and means for selectingvoltage from said resistance network.

EDWIN H. ARMSTRONG.

